1. Field of the Invention
This invention relates to a container made of synthetic resin and to a method for the manufacture thereof. Particularly, this invention relates to a container made of synthetic resin possessing an extremely high gas barrier property and satisfactory transparency and the ability to retain the interior thereof under a high degree of vacuum or pressure stably for a long period of time and to a method for the manufacture of the container. More particularly, this invention relates to a container for holding a gas containing beverage, a blood collecting vessel under a vacuum, a container for holding a chemical agent, or a container for performing a test and to a method for the manufacture of such a container.
2. Description of the Prior Art
Heretofore, containers made of various types of synthetic resins have been in use in various fields. Among these containers are counted those which by nature are used with the interiors thereof kept under a vacuum or a pressure. Containers for gas containing beverages such as beer, cola, and cider are concrete examples. Some of the containers made of synthetic resin are used for holding chemical solutions. Containers for holding transfusion fluids such as fatty transfusion fluid, nutritive drinks containing amino acids, aqueous glucose solution, and physiological saline are concrete exmaples.
When blood is collected from a human body, the method of vacuum blood collection has found popular acceptance because it entails hemolysis and coagulation only to a minimal extent, warrants collection of specimens suffering from contamination or evaporation of water, and, in terms of efficiency, enables preparation for blood collection and management of devices to be simplified. The vacuum blood collecting vessel which is used in the method of vacuum blood collection comprises a tubular container and a pierceable tightly sealing rubber plug. The tightly sealed container has the interior thereof kept in a vacuum. Desired blood collection with this tightly sealed container is attained by having one end of a blood collection needle plunged into the blood vessel and the other end thereof plunged through the rubber plug into the tightly sealed container thereby establishing communication between the interior of the container and the blood vessel and causing the blood to flow into the container by virtue of the negative pressure present therein. In one example of the vacuum blood collecting vessel heretofore in use, a tubular container made of glass which lacks permeability to gas and excels in transparency is used as the tubular container and a plug made of butyl rubber which is insignificantly permeable to gas and pierceable is used as the plug.
Heretofore, a testing device formed by placing a testing chemicals in a container has been used for effecting desired diagnosis by culturing a microorganism present in blood or some other body fluid or detecting any abnormal component in such blood or body fluid. One example of the testing device comprises a container and a body fluid or gel-like culture medium and an anticoagulant held therein.
In the vacuum container of the nature which has been in use, a container made of glass which lacks permeability to gas and enjoys satisfactory transparency has been adpoted as the container body. The container made of glass, however, has the disadvantage that it is liable to sustain breakage while in storage, transportation, or use and, moreover, is heavy. Thus, researches have been conducted on the feasibility of containers made of light and transparent synthetic resin. Since virtually all grades of synthetic resin are permeable to gas to varying extents, containers made of such synthetic resin are invaded by ambient gas such as, for example, air after prolonged storage. Particularly in the case of the vacuum blood collection tube, it is deprived of its ability to effect required collection of blood after prolonged storage because the inner pressure thereof rises owing to the invasion by the ambient gas. Thus, it has been necessary for the tube to be preserved in a vacuum packaged container. The preservation by the use of the vacuum packaged container, however, proves extremely expensive because this container by nature is required to keep the interior thereof under a high degree of vacuum. This container also has the disadvantage that since it is sealed and opened at the expense of much time and labor, it proves quite costly. Then, in the case of the container for a beverage containing carbon dioxide gas, there is the possibility that the carbon dioxide gas component in the beverage will penetrate the wall of the container and diffuse into the ambient air. In the case of the container for a fatty transfusion fluid or an amino acid, the fluid within is degenerated by oxidation with the oxygen contained in the ambient air entering the container. Thus, the adoption of the container made of synthetic resin makes it necessary for this container to be preserved in a vacuum packaged container. The preservation by the use of the vacuum packaged container, however, proves extremely expensive because this container by nature is required to keep the interior thereof under a high degree of vacuum. This container also has the disadvantage that since it is sealed and opened at the expense of much time and labor, it proves quite costly. In the case of the container for an aqueous solution such as aqueous glucose solution or physiological saline solution, there is the disadvantage that since the water within vaporizes and, in the form of steam, penetrates the synthetic resin wall of the container, the aqueous solution suffers from gradual change of concentration.
Further, such plastic container contained chemical solutions, similarly to the conventional containers, are required to undergo sterilization before they are used. Generally the sterilization of such plastic containers is carried out in saturated steam at an elevated temperature. This treatment is called "high-pressure steam sterilization". Even in the case of the container made of a plastic material such as polyvinyl chloride which has low permeability to gas at normal room temperature, when it is subjected to the high-pressure steam sterilization, the permeability of the plastic material is heightened possibly to a point where the oxygen in the atmosphere penetrates the wall of the container of plastic material and causes degeneration of the solution held therein. When the solution is a highly concentrated amino acid transfusion fluid containing tryptophan or a fatty emulsion for transfusion which contains a component susceptible of degeneration by oxygen, the container has a strong possibility of yielding its content to degeneration. There is further the disadvantage that under the ordinary high-pressure steam sterilization, plastic containers are liable to sustain breakage.
In the case of the testing device, there is the disadvantage that the testing chemicals held within are susceptible to degeneration. When the container make of synthetic resin holds a readily oxidizable chemical solution such as, for example, a liquid or gel-like culture medium or an anticoagulant, this chemical solution is degenerated by oxidation with the oxygen contained in the ambient air which enters the container through its wall. Thus, the adoption of this container made of synthetic reain makes it necessary for the container to be preserved within a vacuum packaged container. The preservation by the use of the vacuum packaged container, however, proves extremely expensive because this container by nature is required to keep the interior thereof under a high degree of vacuum. This container also has the disadvantage that since it is sealed and opened at the expense of much time and labor, it proves quite costly. When the aforementioned testing chemical is an aqueous solution, there is the disadvantage that since the water held within vaporizes and, in the form of steam, finds its way through the wall of the container made of synthetic resin, the concentration of the aqueous solution varies with elapse of time.
An object of this invention, therefore, is to provide a novel container made of synthetic resin of repressed permeability to gas and intended to hold its content under a high degree of vacuum or pressure and a method for the manufacture of the container.
Another object of this invention is to provide a container made of synthetic resin which possesses a high gas barrier property and satisfactory transparency and the ability to retain its content under a high degree of vacuum or pressure stably for a long period of time and a method for the manufacture of the container.
Yet another object of this invention is to provide a vacuum or pressure container made of transparent synthetic resin having no possibility of sustaining breakage and possessing an extremely high gas barrier property and a method for the manufacture of the container.
Still another object of this invention is to provide containers made of synthetic resin and used for holding bicarbonate type beverages, vacuum blood collecting vessel, chemical agent containers, and testing devices and a method for the manufacture of such containers.